1. Field of the Invention
The present invention relates to a cylinder-type linear motor having a permanent magnet in a moving part section and a plurality of ring-shaped coils in a fixed part section, and a moving part thereof.
2. Description of Related Art
FIG. 11 is a sectional view of a two-phase cylinder-type linear motor that has been known conventionally.
In FIG. 11, a moving part 100 of the cylinder-type linear motor includes a linear motion shaft 101 reciprocating in the axial direction, a cylindrical moving part yoke 102 mounted on the linear motion shaft 101, and a plurality of ring-shaped permanent magnets 103 arranged on the outer peripheral surface of the moving part yoke 102 in a magnetized manner such as to adopt an alternate polarity with a magnetic pole pitch P in the axial direction. Also, a fixed part core 201 of a fixed part 200 has ring-shaped yoke portions 202 each having a smaller inside diameter and ring-shaped yoke portions 203 each having a larger inside diameter, both yoke portions being laminated alternately in the axial direction. As a result, on the inner peripheral surface of the fixed part 201, a large number of ring-shaped tooth portions 204 and ring-shaped groove portions 205 are formed in the axial direction with an equal pitch (P/2). In the ring-shaped groove portions 205, ring-shaped coils 206, 207, . . . , 213 are disposed in the phase order of A phase and B phase. Therefore, the ring-shaped coils 206, 208, 210 and 212 disposed alternately are connected to each other to form an A-phase winding, and the remaining coils 207, 209, 211 and 213 are also connected to each other to form a B-phase winding.
An axial length M of a moving part core section is longer than an axial length K of a fixed core section, and therefore is an axial length in which the moving part and the fixed part face each other, namely, a thrust contribution length K. Also, a stroke length S is expressed by (M−K). From FIG. 11, the travel range length of the moving part is expressed by (K+2S), namely, (thrust contribution length+2×stroke length S). The total motor length is set so as to satisfy the travel range length of the moving part. As the related art, Japanese Patent Provisional Publication No. 7-107732 and Japanese Patent Provisional Publication No. 5-15139 can be cited.